There are many situations where it is desirable to be able to scan a light beam in a particular direction. For example, a two-dimensional image of an object may be generated by scanning a light beam in two dimensions and capturing resulting light emanating from the object, e.g., reflected by a fluorescent light, with a point detector whose output is synchronized with the scanning light beam to produce image data. This technique can also be extended to three dimensions. A particular case of this is confocal imaging, where a scanning light beam has a focal point that is optically conjugate with a pinhole spatial filter in front of the detector, which serves to reduce the image noise from scattered light.
One known way to scan a light beam is to use a pair of mirrors mounted on respective galvanometers so that the axis of rotation of each galvanometer lies in the plane of its respective mirror and they are disposed askew, typically perpendicular, to one another such that a light beam from a light source strikes and is reflected off a first mirror toward a second mirror, where it is reflected from the second mirror in the ultimate desired direction.
For good performance, galvanometric scanners need to be used with and closely matched to other optics included in a scanning system. The critical component of the system typically is a scan lens that forms the input optic and translates the angular deflection of the scan beam by the rotating mirrors mounted on galvanometers into a linearly moving point in the plan of a virtual image, while at the same time illuminating the full back-aperture of an objective lens that forms the output optic. This is a difficult design problem that is compounded by the fact that each galvanometer has its own pivot point at a different distance from the virtual image plane, which typically necessitates the use of relay optics between each galvanometer. Not only does the design and production of a good scan lens exceed the capabilities of most laboratories, but the scan lens is also very specific to the objective or other “front end” optical device for which the system is designed and may be limited to just one type of optical device, such as, for example, a microscope, an endoscope or an opthalmoscope.
It would be desirable to have a beam scanning method and system that may be used with a variety of front end optical devices and does not require complicated lens design.
Generally, there are applications for optical beam scanners where locating the center of rotation of the beam in free space away from any mirror or structure would be advantageous. In conventional beam steering designs that is not possible. The rotation of a beam typically occurs at fold mirror face and the pivot point is located on the mirror face coincident with the axis of rotation of the mirror.
It would also be desirable to have a beam scanning method and system that produces a scanning beam whose center of rotation is located in free space away from any mirror or structure.